Can a deer eat a weasel?

Answer 1

It can, but only as a scavenger. A weasel might have a nibble if it'd find an already dead deer, but it's way too small to be able to kill a deer itself.

There is, however, a species of weasel that is capable of killing and eating a deer, and that is the wolverine.

Answer 2

No. Deer are vegetarians/herbivores and their teeth are not made for that. Also, they would not be able to digest the weasel as they are ruminants.